memory.h

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/* *****************************************************************************
 * kblib is a general utility library for C++14 and C++17, intended to provide
 * performant high-level abstractions and more expressive ways to do simple
 * things.
 *
 * Copyright (c) 2021 killerbee
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 * ****************************************************************************/
 
#ifndef MEMORY_H
#define MEMORY_H
 
#include "algorithm.h"
#include "tdecl.h"
 
#include <utility>
#include <vector>
 
namespace kblib {
 
template <typename T, bool = std::is_class<T>::value>
struct null_construct {
   null_construct() noexcept(std::is_nothrow_default_constructible<T>::value)
       : t{} {}
 
   T t;
 
   operator T&() noexcept { return t; }
   operator const T&() const noexcept { return t; }
};
 
template <typename T>
struct null_construct<T, true> : public T {
   null_construct() noexcept(std::is_nothrow_default_constructible<T>::value)
       : T{} {}
};
 
#if __cpp_nontype_template_parameter_auto
template <auto FunPtr>
struct fun_ptr_deleter;
 
template <typename Arg, void (*FunPtr)(Arg)>
struct fun_ptr_deleter<FunPtr> {
   auto operator()(Arg arg) const -> void { return FunPtr(arg); }
};
#endif
 
namespace detail_memory {
 
   template <typename D, typename T, typename V = void>
   struct filter_deleter_pointer {
      using type = T*;
   };
 
   template <typename D, typename T>
   struct filter_deleter_pointer<D, T, void_t<typename D::pointer>> {
      using type = typename std::remove_reference<D>::type::pointer;
   };
 
   template <typename D, typename T>
   using filter_deleter_pointer_t = typename filter_deleter_pointer<D, T>::type;
 
   template <typename T,
             bool = std::is_class<T>::value and not std::is_final<T>::value,
             bool
             = std::is_object<typename std::remove_reference<T>::type>::value>
   struct as_base_class;
 
   template <typename T>
   struct as_base_class<T, false, true> {
      T base_;
      auto base() noexcept -> T& { return base_; }
      auto base() const noexcept -> const T& { return base_; }
      explicit operator T&() noexcept { return base(); }
      explicit operator const T&() const noexcept { return base(); }
   };
 
   template <typename T>
   struct as_base_class<T, true, true> : T {
      auto base() noexcept -> T& { return *this; }
      auto base() const noexcept -> const T& { return *this; }
      using T::T;
      as_base_class(const T& t,
                    enable_if_t<std::is_copy_constructible<T>::value,
                                as_base_class*> = nullptr) //
          noexcept(std::is_nothrow_copy_constructible<T>::value)
          : T(t) {}
      as_base_class(T&& t, enable_if_t<std::is_move_constructible<T>::value,
                                       as_base_class*> = nullptr) //
          noexcept(std::is_nothrow_move_constructible<T>::value)
          : T(std::move(t)) {}
   };
 
#if KBLIB_USE_CXX17
   template <typename R, typename A, bool E>
   struct as_base_class<R (&)(A) noexcept(E), false, false> {
      using type = R(A) noexcept(E);
      type* base_;
      auto base() const noexcept -> type& { return *base_; }
      explicit operator type&() const noexcept { return base(); }
   };
#else
   template <typename R, typename A>
   struct as_base_class<R (&)(A), false, false> {
      using type = R(A);
      type* base_;
      auto base() const noexcept -> type& { return *base_; }
      explicit operator type&() const noexcept { return base(); }
   };
#endif
 
   template <typename T>
   struct as_base_class<T&, false, true> {
      std::reference_wrapper<T> base_;
 
      auto base() noexcept -> T& { return base_; }
      auto base() const noexcept -> const T& { return base_; }
 
      explicit operator T&() noexcept { return base(); }
      explicit operator const T&() const noexcept { return base(); }
   };
 
   struct noop_t {
      auto operator()() const noexcept -> void {}
   };
   struct value_init {};
 
   template <typename T, typename Construct = noop_t, typename Destroy = noop_t>
   struct rule_zero : as_base_class<T> {
      template <typename... Args>
      rule_zero(Args&&... args)
          : as_base_class<T>(std::forward<Args>(args)...) {}
   };
 
   template <typename T, typename D>
   struct on_destroy
       : as_base_class<T>
       , as_base_class<D> {
      on_destroy() noexcept = default;
      on_destroy(const on_destroy&) noexcept(
          std::is_nothrow_copy_constructible<T>::value and
              std::is_nothrow_copy_constructible<D>::value)
          = default;
      on_destroy(on_destroy&&) noexcept(
          std::is_nothrow_move_constructible<T>::value and
              std::is_nothrow_move_constructible<D>::value)
          = default;
      on_destroy& operator=(const on_destroy&) noexcept(
          std::is_nothrow_copy_assignable<T>::value and
              std::is_nothrow_copy_assignable<D>::value)
          = default;
      on_destroy& operator=(on_destroy&&) noexcept(
          std::is_nothrow_move_assignable<T>::value and
              std::is_nothrow_move_assignable<D>::value)
          = default;
 
      using as_base_class<T>::base;
      operator T&() noexcept { return base(); }
      operator const T&() const noexcept { return base(); }
 
      ~on_destroy() {
         (invoke)(static_cast<D&&>(*this), static_cast<T&&>(*this));
      }
   };
 
} // namespace detail_memory
 
template <typename T>
class live_ptr;
 
template <typename T>
class live_wrapper {
 public:
   live_ptr<T> ref();
   live_ptr<const T> ref() const;
   live_ptr<const T> cref() const;
 
   T data;
 
   struct _destroy {
      auto operator()(std::vector<live_wrapper**>&& self) const noexcept
          -> void {
         for (auto p : self) {
            if (p) {
               *p = nullptr;
            }
         }
      }
   };
 
   null_construct<
       detail_memory::on_destroy<std::vector<live_wrapper**>, _destroy>>
       _observers{};
};
 
template <typename T>
class live_wrapper<const T> : public live_wrapper<T> {};
 
namespace detail_memory {
 
   template <typename T>
   struct template_param;
   template <template <typename T> class C, typename T>
   struct template_param<C<T>> {
      using type = T;
   };
 
   template <typename D>
   struct live_ptr_base {
    private:
      using T = typename template_param<D>::type;
      using mT = typename std::remove_const<T>::type;
 
    public:
      auto operator*() noexcept -> T& { return obj->data; }
      auto operator*() const noexcept -> const T& { return obj->data; }
 
      auto operator->() noexcept -> T* { return &obj->data; }
      auto operator->() const noexcept -> const T* { return &obj->data; }
 
      operator bool() const noexcept { return obj; }
 
      friend auto operator==(const D& lhs, std::nullptr_t) -> bool {
         return not lhs;
      }
      friend auto operator==(std::nullptr_t, const D& rhs) -> bool {
         return not rhs;
      }
 
      friend auto operator==(const D& lhs, const D& rhs) -> bool {
         return lhs.obj == rhs.obj;
      }
 
      friend auto operator==(const D& lhs, const T* rhs) -> bool {
         if (not lhs and not rhs) {
            return true;
         } else {
            return lhs and &lhs.obj->data == rhs;
         }
      }
      friend auto operator==(const T* lhs, const D& rhs) -> bool {
         if (not rhs and not lhs) {
            return true;
         } else {
            return rhs and &rhs.obj->data == lhs;
         }
      }
 
      live_ptr_base() noexcept = default;
      live_ptr_base(live_wrapper<mT>* p)
          : obj{p} {
         add();
      }
      auto operator=(const live_ptr_base& o) noexcept -> live_ptr_base& {
         rem();
         obj = o.obj;
         add();
         return *this;
      }
      auto operator=(live_ptr_base&& o) noexcept -> live_ptr_base& {
         rem();
         move(o);
         return *this;
      }
 
      live_ptr_base(const live_ptr_base& o)
          : obj{o.obj} {
         add();
      }
      live_ptr_base(live_ptr_base&& o) noexcept { move(o.as_D()); }
      ~live_ptr_base() { rem(); }
 
      auto operator=(const D& o) -> D& {
         rem();
         obj = o.obj;
         add();
         return as_D();
      }
      auto operator=(D&& o) noexcept -> D& {
         this->rem();
         this->move(o);
         return as_D();
      }
 
    protected:
      auto add() -> void { obj->_observers.base().push_back(&obj); }
      auto rem() -> void {
         if (obj) {
            erase(obj->_observers.base(), &obj);
         }
      }
      auto move(D& o) -> void {
         if ((obj = std::exchange(o.obj, nullptr))) {
            std::replace(obj->_observers.base().begin(),
                         obj->_observers.base().end(), &o.obj, &obj);
         }
      }
      mutable live_wrapper<mT>* obj = nullptr;
 
    private:
      auto as_D() noexcept -> D& { return static_cast<D&>(*this); }
      auto as_D() const noexcept -> const D& {
         return static_cast<const D&>(*this);
      }
   };
} // namespace detail_memory
 
template <typename T>
class live_ptr : public detail_memory::live_ptr_base<live_ptr<T>> {
   using base = detail_memory::live_ptr_base<live_ptr<T>>;
 
 public:
   using value_type = T;
 
   live_ptr() = default;
   live_ptr(const live_ptr& o) = default;
   live_ptr(live_ptr&& o) noexcept = default;
   auto operator=(const live_ptr& o) -> live_ptr& = default;
   auto operator=(live_ptr&& o) noexcept -> live_ptr& = default;
 
   explicit live_ptr(live_wrapper<T>& o)
       : base{&o} {
      this->add();
   }
   auto operator=(live_wrapper<T>& o) -> live_ptr& {
      this->rem();
      this->obj = &o;
      this->add();
      return *this;
   }
 
   ~live_ptr() = default;
 
 private:
   friend class live_ptr<const T>;
};
 
template <typename mT>
class live_ptr<const mT>
    : public detail_memory::live_ptr_base<live_ptr<const mT>> {
   using base = detail_memory::live_ptr_base<live_ptr<const mT>>;
 
 public:
   using T = const mT;
   using value_type = T;
   live_ptr() = default;
   live_ptr(const live_ptr<T>& o) = default;
   live_ptr(const live_ptr<mT>& o)
       : base{o.obj} {}
   live_ptr(live_ptr<T>&& o) noexcept = default;
   live_ptr(live_ptr<mT>&& o) noexcept { this->move(o); }
   auto operator=(const live_ptr<T>& o) -> live_ptr& = default;
   auto operator=(live_ptr<T>&& o) noexcept -> live_ptr& = default;
 
   auto operator=(const live_ptr<mT>& o) -> live_ptr& {
      this->obj = o.obj;
      this->add();
      return *this;
   }
   auto operator=(live_ptr<mT>&& o) noexcept -> live_ptr& {
      this->obj = o.obj;
      this->add();
      return *this;
   }
 
   explicit live_ptr(const live_wrapper<mT>& o)
       : base{&o} {
      this->add();
   }
   auto operator=(const live_wrapper<mT>& o) -> live_ptr& {
      this->rem();
      this->obj = &o;
      this->add();
      return *this;
   }
 
   ~live_ptr() = default;
};
 
template <typename T>
live_ptr<T> live_wrapper<T>::ref() {
   return live_ptr<T>{*this};
}
 
template <typename T>
live_ptr<const T> live_wrapper<T>::ref() const {
   return live_ptr<const T>{*this};
}
 
template <typename T>
live_ptr<const T> live_wrapper<T>::cref() const {
   return live_ptr<const T>{*this};
}
 
// cond_ptr: A pointer which can either uniquely own its referent, or which can
// be a non-owning reference. Note that custom deleter support is not present;
// however it will not implicitly strip a deleter from a unique_ptr.
 
template <typename T, typename Deleter = std::default_delete<T>>
class cond_ptr : private detail_memory::as_base_class<Deleter> {
   using d_base = detail_memory::as_base_class<Deleter>;
 
 public:
   using pointer = detail_memory::filter_deleter_pointer_t<Deleter, T>;
   using element_type = T;
   using deleter_type = Deleter;
 
#if 0
   static_assert(std::is_nothrow_invocable<Deleter&, pointer>::value,
                 "cond_ptr<T> requires that get_deleter not throw exceptions.");
#endif
 
   using unique = std::unique_ptr<T, Deleter>;
 
   cond_ptr() noexcept = default;
   cond_ptr(std::nullptr_t) noexcept {}
 
   explicit cond_ptr(T* p, bool owner = false,
                     std::decay_t<Deleter> del = {}) noexcept
       : d_base{std::move(del)}
       , ptr_(p)
       , owns_(owner) {}
   explicit cond_ptr(T* p, std::decay_t<Deleter> del) noexcept
       : d_base{std::move(del)}
       , ptr_(p) {}
 
   cond_ptr(unique&& p) noexcept
       : d_base{p.get_deleter()}
       , ptr_(p.release())
       , owns_(ptr_) {}
 
   cond_ptr(const cond_ptr& other) = delete;
   // cond_ptr(const cond_ptr& other) noexcept
   //     : d_base{other.get_deleter()}, ptr_(other.ptr_) {}
   cond_ptr(cond_ptr&& other) noexcept
       : d_base{other.get_deleter()}
       , ptr_(other.ptr_)
       , owns_(std::exchange(other.owns_, false)) {}
 
   KBLIB_NODISCARD static auto adopt(T* p) noexcept -> cond_ptr {
      return {p, true};
   }
   KBLIB_NODISCARD static auto adopt(T* p, deleter_type del) noexcept
       -> cond_ptr {
      return {p, true, del};
   }
 
   auto operator=(const cond_ptr& rhs) & -> cond_ptr& = delete;
   //  auto operator=(const cond_ptr& rhs) & noexcept -> cond_ptr& {
   //    if (owns_) {
   //       get_deleter()(ptr_);
   //    }
   //    owns_ = false;
   //    ptr_ = rhs.release();
   //    return *this;
   // }
   auto operator=(cond_ptr&& rhs) & noexcept -> cond_ptr& {
      if (owns_) {
         get_deleter()(ptr_);
      }
      owns_ = rhs.owns();
      static_cast<d_base&>(*this) = {std::move(rhs.get_deleter())};
      ptr_ = rhs.release();
      return *this;
   }
   auto operator=(unique&& rhs) -> cond_ptr& {
      static_cast<d_base&>(*this) = {std::move(rhs.get_deleter())};
      ptr_ = rhs.release();
      owns_ = bool(ptr_);
      return *this;
   }
 
   KBLIB_NODISCARD auto to_unique() && noexcept -> unique {
      if (owns_) {
         return {release(), std::move(get_deleter())};
      } else {
         return {nullptr, get_deleter()};
      }
   }
 
   explicit operator unique() && noexcept {
      return std::move(*this).to_unique();
   }
 
   ~cond_ptr() noexcept {
      if (owns_ and ptr_) {
         get_deleter()(ptr_);
      }
   }
 
   KBLIB_NODISCARD auto weak() const& noexcept -> cond_ptr {
      return cond_ptr{ptr_, false};
   }
 
   KBLIB_NODISCARD auto owns() const noexcept -> bool { return owns_; }
   KBLIB_NODISCARD auto release() & noexcept -> T* {
      owns_ = false;
      return std::exchange(ptr_, nullptr);
   }
 
   KBLIB_NODISCARD auto get_deleter() noexcept -> Deleter& {
      return this->d_base::base();
   }
 
   KBLIB_NODISCARD auto get_deleter() const noexcept -> const Deleter& {
      return this->d_base::base();
   }
 
   auto reset(T* p = nullptr, bool owner = false,
              std::decay_t<Deleter> del = {}) & noexcept -> void {
      if (owns_) {
         get_deleter()(ptr_);
      }
      ptr_ = p;
      owns_ = owner;
      get_deleter() = std::move(del);
   }
   auto reset(T* p, std::decay_t<Deleter> del = {}) & noexcept -> void {
      if (owns_) {
         get_deleter()(ptr_);
      }
      ptr_ = p;
      owns_ = false;
      get_deleter() = std::move(del);
   }
 
   auto swap(cond_ptr& other) noexcept(
       fakestd::is_nothrow_swappable<Deleter>::value) -> void {
      using std::swap;
      swap(ptr_, other.ptr_);
      swap(owns_, other.owns_);
      swap(get_deleter(), other.get_deleter());
   }
 
   KBLIB_NODISCARD auto get() & noexcept -> T* { return ptr_; }
 
   KBLIB_NODISCARD auto get() const& noexcept -> const T* { return ptr_; }
 
   KBLIB_NODISCARD explicit operator bool() const noexcept { return ptr_; }
 
   KBLIB_NODISCARD auto operator*() & noexcept -> T& { return *ptr_; }
 
   KBLIB_NODISCARD auto operator*() const& noexcept -> const T& {
      return *ptr_;
   }
 
   KBLIB_NODISCARD auto operator->() & noexcept -> T* { return ptr_; }
 
   KBLIB_NODISCARD auto operator->() const& noexcept -> const T* {
      return ptr_;
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(
       const cond_ptr& lhs, const cond_ptr& rhs) noexcept -> bool {
      return lhs.ptr_ == rhs.ptr_;
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(
       const unique& lhs, const cond_ptr& rhs) noexcept -> bool {
      return lhs.get() == rhs.ptr_;
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(const cond_ptr& lhs,
                                                    const unique& rhs) noexcept
       -> bool {
      return lhs.ptr_ == rhs.get();
   }
 
 private:
   T* ptr_ = nullptr;
   bool owns_ = false;
};
 
template <typename T, typename Deleter>
class cond_ptr<T[], Deleter> : private detail_memory::as_base_class<Deleter> {
   using d_base = detail_memory::as_base_class<Deleter>;
 
 public:
   using pointer = detail_memory::filter_deleter_pointer_t<Deleter, T>;
   using element_type = T;
   using deleter_type = Deleter;
 
#if 0
   static_assert(std::is_nothrow_invocable<Deleter&, pointer>::value,
                 "cond_ptr<T[]> requires that deleter not throw exceptions.");
#endif
 
   using unique = std::unique_ptr<T[], Deleter>;
 
   cond_ptr() noexcept = default;
   cond_ptr(std::nullptr_t) noexcept {}
 
   explicit cond_ptr(T* p, bool owner = false,
                     std::decay_t<Deleter> del = {}) noexcept
       : d_base{std::move(del)}
       , ptr_(p)
       , owns_(owner) {}
   explicit cond_ptr(T* p, std::decay_t<Deleter> del) noexcept
       : d_base{std::move(del)}
       , ptr_(p) {}
 
   cond_ptr(unique&& p) noexcept
       : d_base{p.get_deleter()}
       , ptr_(p.release())
       , owns_(ptr_) {}
 
   cond_ptr(const cond_ptr& other) = delete;
   // cond_ptr(const cond_ptr& other) noexcept
   //     : d_base{other.get_deleter()}, ptr_(other.ptr_) {}
   cond_ptr(cond_ptr&& other) noexcept
       : d_base{other.get_deleter()}
       , ptr_(other.ptr_)
       , owns_(std::exchange(other.owns_, false)) {}
 
   KBLIB_NODISCARD static auto adopt(T* p) noexcept -> cond_ptr {
      return {p, true};
   }
   KBLIB_NODISCARD static auto adopt(T* p, deleter_type del) noexcept
       -> cond_ptr {
      return {p, true, del};
   }
 
   auto operator=(const cond_ptr& rhs) & -> cond_ptr& = delete;
   //  auto operator=(const cond_ptr& rhs) & noexcept -> cond_ptr& {
   //    if (owns_) {
   //       get_deleter()(ptr_);
   //    }
   //    owns_ = false;
   //    ptr_ = rhs.release();
   //    return *this;
   // }
   auto operator=(cond_ptr&& rhs) & noexcept -> cond_ptr& {
      if (owns_) {
         get_deleter()(ptr_);
      }
      owns_ = rhs.owns();
      ptr_ = rhs.release();
      return *this;
   }
   auto operator=(unique&& rhs) -> cond_ptr& {
      ptr_ = rhs.release();
      owns_ = bool(ptr_);
      get_deleter() = std::move(rhs.get_deleter());
      return *this;
   }
 
   KBLIB_NODISCARD auto to_unique() && noexcept -> unique {
      if (owns_) {
         return {release(), get_deleter()};
      } else {
         return nullptr;
      }
   }
 
   explicit operator unique() && noexcept {
      return std::move(*this).to_unique();
   }
 
   ~cond_ptr() noexcept {
      if (owns_) {
         get_deleter()(ptr_);
      }
   }
 
   KBLIB_NODISCARD auto weak() const& noexcept -> cond_ptr {
      return cond_ptr{ptr_, false};
   }
 
   KBLIB_NODISCARD auto owns() const noexcept -> bool { return owns_; }
   KBLIB_NODISCARD auto release() & noexcept -> T* {
      owns_ = false;
      return std::exchange(ptr_, nullptr);
   }
 
   KBLIB_NODISCARD auto get_deleter() noexcept -> Deleter& { return *this; }
 
   KBLIB_NODISCARD auto get_deleter() const noexcept -> const Deleter& {
      return *this;
   }
 
   auto reset(T* p = nullptr, bool owner = false,
              std::decay_t<Deleter> del = {}) & noexcept -> void {
      if (owns_) {
         get_deleter()(ptr_);
      }
      ptr_ = p;
      owns_ = owner;
      get_deleter() = std::move(del);
   }
   auto reset(T* p, std::decay_t<Deleter> del = {}) & noexcept -> void {
      if (owns_) {
         get_deleter()(ptr_);
      }
      ptr_ = p;
      owns_ = false;
      get_deleter() = std::move(del);
   }
 
   auto swap(cond_ptr& other) -> void {
      std::swap(ptr_, other.ptr_);
      std::swap(owns_, other.owns_);
      std::swap(get_deleter(), other.get_deleter());
   }
 
   KBLIB_NODISCARD auto get() & noexcept -> T* { return ptr_; }
 
   KBLIB_NODISCARD auto get() const& noexcept -> const T* { return ptr_; }
 
   explicit operator bool() const noexcept { return ptr_; }
 
   KBLIB_NODISCARD T& operator[](std::size_t index) & noexcept {
      return ptr_[index];
   }
 
   KBLIB_NODISCARD const T& operator[](std::size_t index) const& noexcept {
      return ptr_[index];
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(
       const cond_ptr& lhs, const cond_ptr& rhs) noexcept -> bool {
      return lhs.ptr_ == rhs.ptr_;
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(
       const unique& lhs, const cond_ptr& rhs) noexcept -> bool {
      return lhs.get() == rhs.ptr_;
   }
 
   KBLIB_NODISCARD friend constexpr auto operator==(const cond_ptr& lhs,
                                                    const unique& rhs) noexcept
       -> bool {
      return lhs.ptr_ == rhs.get();
   }
 
 private:
   T* ptr_ = nullptr;
   bool owns_ = false;
};
 
template <typename T, typename Deleter>
KBLIB_NODISCARD auto make_cond_ptr(std::unique_ptr<T, Deleter>&& arg) noexcept
    -> cond_ptr<T, Deleter> {
   return cond_ptr<T>(std::move(arg));
}
 
template <typename T>
KBLIB_NODISCARD auto make_cond_ptr(T* arg, bool owner = false) noexcept
    -> cond_ptr<T> {
   return cond_ptr<T>(arg, owner);
}
 
template <typename T, typename Deleter>
KBLIB_NODISCARD auto make_cond_ptr(T* arg, Deleter del) noexcept
    -> cond_ptr<T, Deleter> {
   return cond_ptr<T, Deleter>(arg, del);
}
 
template <typename T, typename Deleter>
KBLIB_NODISCARD auto make_cond_ptr(T* arg, bool owner, Deleter del) noexcept
    -> cond_ptr<T, Deleter> {
   return cond_ptr<T, Deleter>(arg, owner, del);
}
 
} // namespace kblib
 
#endif // MEMORY_H